The proposed research is a study of an inherited hemolytic anemia, "xerocytosis". Red blood cells from patients with this disease exhibit an accelerated passive K ion efflux resulting in cellular dehydration. Cellular 2,3-diphosphoglycerate levels are low despite the anemia. Intracellular pH and hemoglobin are normal, and no defect in metabolism has been established. Xerocyte membranes will be characterized to define the molecular basis for abnormal function. Parameters of characterization will be high-resolution analytic fractionation of membrane proteins, accessibility to surface labeling reagents, pattern of protein cross-linking, content of membrane-associated enzymes, susceptibility to lipid peroxidation, and capacity to reseal. Metabolism in xerocytes will be examined, with emphasis on reactions involved in maintenance of 2,3-DPG. Kinetic parameters of key enzymes, levels of metabolic intermediates, flux of radioisotope tracers through 2,3-DPG, and cation effects on reaction rates will be studied. Aspects of membrane-cytoplasm interaction will be investigated, with emphasis on identification of factors responsible for elevated retention of glyceraldehyde-3-phosphate dehydrogenase in xerocyte membranes. Effects of normal and xerocyte cytoplasm on ghost resealing will be studied. Studies of membrane biogenesis in cultures of erythroid cells from peripheral blood and bone marrow will be undertaken, with the objective of describing stages of membrane protein synthesis and identifying the time of earliest expression of altered membrane structure and function in xerocytosis.